How to Install an Audi A4#039;s Trailer Hitch

1. Locate the three retaining screws that attach the plastic bumper fascia on the rear of the car to the underside of the trunk compartment pan. Remove the screws with a Phillips screwdriver, and place them aside.
2. Open the trunk lid, and raise the cargo mat. Remove the spare tire wing nut by hand, then remove the spare tire and jack from the trunk and place them aside. Locate the two drain plugs at the rear of the trunk pan where the spare resided by prying them out with a slotted screwdriver. Keep the plugs for future use, or discard them.
3. Find the center of the rear bumper fascia using a measuring tape. Mark a notch at the bottom center of the fascia 3.25 inches wide and 3 inches deep with a felt-tipped pen. Cut the notch out carefully using a sharp utility knife. Use care when making this cut, as it will be visible from the rear of the car.
4. Pull the rear fascia down and to the rear of the car slightly to reveal the ends of the rear frame rails. Place a bolt plate on top of one of the rails, ensuring the two mounting holes in the plate straddle the frame rail. Insert a carriage bolt into each of the mounting holes so the threaded end of the bolt is points downward. Repeat this procedure on the other frame rail.
5. Raise the hitch into place on the rear of the car, lining up the rear mounting holes in the hitch with the four carriage bolts installed earlier. Place a washer and retaining nut onto the end of each carriage bolt, and tighten them finger tight.
6. Place spacer blocks over the two drain holes inside the spare tire compartment in the trunk, then place a carriage bolt into the hole in each spacer. Check to ensure the threaded end of each bolt protrudes through the forward mounting holes in the hitch. Place a washer and retaining nut onto the ends of each bolt. Tighten these nuts and the four installed earlier with a torque wrench to the tightness specified in the hitch installation instructions.
7. Push the rear fascia into place under the car, and tighten the retaining screws with a Phillips screwdriver. Replace the tire jack and spare tire, and secure them. Pull the cargo mat back over the spare, and close the trunk lid.